Positive active material for nonaqueous electrolyte secondary battery, method of producing positive active material for nonaqueous electrolyte secondary battery, positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery

Abstract

Disclosed is a positive active material for a nonaqueous electrolyte secondary battery containing a lithium transition metal composite oxide, in which the lithium transition metal composite oxide has an α-NaFeO 2 structure, a molar ratio Li/Me of Li and a transition metal (Me) of 1.05≤Li/Me≤1.4, and a porosity of 5 to 15%.

1 . A positive active material for a nonaqueous electrolyte secondary battery containing a lithium transition metal composite oxide,
 wherein   the lithium transition metal composite oxide has an α-NaFeO 2  structure,   a molar ratio Li/Me of Li and a transition metal (Me) of 1.05≤Li/Me≤1.4, and   a porosity of 5 to 15%.   
     
     
         2 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 1 , wherein the lithium transition metal composite oxide contains Ni and Mn or Ni, Co, and Mn as the transition metals (Me). 
     
     
         3 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 1 , wherein using lithium metal as a counter electrode,
 (i) charge and discharge in which an end-of-charge voltage is 4.6 V and an end-of-discharge voltage is 2.0 V, and   (ii) charge and discharge in which the end-of-charge voltage is 4.45 V and the end-of-discharge voltage is 2.0 V are performed in this order, and   an electric amount is 200 mAh/g or more in the discharge of (ii).   
     
     
         4 . A method of producing a positive active material for a nonaqueous electrolyte secondary battery containing a lithium transition metal composite oxide, comprising
 mixing a lithium compound with a transition metal hydroxide precursor and firing the mixture at 750 to 1000° C. to prepare the lithium transition metal composite oxide having an α-NaFeO 2  structure, a molar ratio Li/Me of Li and a transition metal (Me) of 1.05≤Li/Me≤1.4, and a porosity of 5 to 15%.   
     
     
         5 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 4 , wherein the transition metal hydroxide precursor contains Ni and Mn or Ni, Co, and Mn as the transition metals (Me) and is a mixture of αMe(OH) 2  and βMe(OH) 2 . 
     
     
         6 . A positive electrode for a nonaqueous electrolyte secondary battery containing the positive active material according to  claim 1 . 
     
     
         7 . A nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery according to  claim 6 . 
     
     
         8 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 1 , wherein the molar ratio Li/Me of Li and the transition metal (Me) is 1.1 or more and 1.35 or less. 
     
     
         9 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 2 , wherein a molar ratio Mn/Me of Mn to the transition metal element Me is 0.35 or more and less than 0.6. 
     
     
         10 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 2 , wherein a molar ratio Co/Me of Co to the transition metal element Me is 0 or more and 0.35 or less. 
     
     
         11 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 2 , wherein a molar ratio Ni/Me of Ni to the transition metal element Me is 0.2 or more and 0.6 or less. 
     
     
         12 . The positive active material for a nonaqueous electrolyte secondary battery according to  claim 2 , wherein
 the molar ratio Li/Me of Li and the transition metal (Me) is 1.1 or more and 1.4 or less,   a molar ratio Mn/Me of Mn to the transition metal element Me is 0.4 or more and less than 0.55,   a molar ratio Co/Me of Co to the transition metal element Me is 0 or more and 0.15 or less, and   a molar ratio Ni/Me of Ni to the transition metal element Me is 0.3 or more and 0.55 or less.   
     
     
         13 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 4 , wherein the molar ratio Li/Me of Li and the transition metal (Me) is 1.1 or more and 1.35 or less. 
     
     
         14 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 5 , wherein a molar ratio Mn/Me of Mn to the transition metal element Me is 0.35 or more and less than 0.6. 
     
     
         15 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 5 , wherein a molar ratio Co/Me of Co to the transition metal element Me is 0 or more and 0.35 or less. 
     
     
         16 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 5 , wherein a molar ratio Ni/Me of Ni to the transition metal element Me is 0.2 or more and 0.6 or less. 
     
     
         17 . The method of producing a positive active material for a nonaqueous electrolyte secondary battery according to  claim 5 , wherein
 the molar ratio Li/Me of Li and the transition metal (Me) is 1.1 or more and 1.4 or less,   a molar ratio Mn/Me of Mn to the transition metal element Me is 0.4 or more and less than 0.55,   a molar ratio Co/Me of Co to the transition metal element Me is 0 or more and 0.15 or less, and   a molar ratio Ni/Me of Ni to the transition metal element Me is 0.3 or more and 0.55 or less.